Intra-Body Communication Channel Modeling and High Performance IBC Transceiver System Design Based on Advanced Techniques.

摘要

Nowadays, with the invention and proliferation of smart wearable electronic devices like cell phones, smart watches and glasses, bio-medical sensors, etc, off-air communication techniques such as capacitive coupling used in these devices, have gained a lot of attention in the research community. As a major branch of Body Area Network, Intra-Body Communication (IBC) uses the human body as a communication medium to implement data transmission between various wearable devices. Comparing with other conventional wireless techniques, IBC offers the advantages of low radiation, low power consumption, high data rate, wide bandwidth, small area and privacy. The targets of this thesis are IBC body communication channel modeling and its high performance transceiver system circuit design, meanwhile realizing the data transmission through human body channel.;Firstly, the first contribution of this thesis is a new human body cascaded network model that is based on a transmission line theory and which uses general linear tissue electrophysiological parameters. Also, more accurate and simpler computations make it more suitable for general IBC channel estimation, transceiver system optimization and communication scheme evaluation. By using the ABCD cascaded matrix, all of the components contained in the transmission path are taken into account and computed, including electrode parasitic impedance, the body channel and the parasitic return capacitor. The comparison between simulation and measurement results also proves the feasibility of the proposed model. Furthermore, to optimize IBC transmission performance, an impedance matching scheme is adopted as well. The power gain can be improved by up to 16dB using the proposed model. This work greatly reduces the gain requirements of communication receiver design, which further relax the specifications of IBC receiver design.;Secondly, a low power, long transmission distance, high data rate IBC analog receiver front end is implemented. 1). Switched-capacitor filters based on sampling rate boosting technique are proposed in the receiver front end design for higher accuracy and data rate. 2). A novel receiver front end topology is proposed to further enhance the IBC performance. The new approach is designed and fabricated in a standard 180nm CMOS process. Measurement results show that it can successfully transmit data spanning the whole human body, around 180cm, which is one of the longest transmission distances reported in related literatures. Furthermore, it reaches a maximum data rate of 2.5Mb/s with a bit error rate less than 10-7 and consumes 5.4mW from a 1.8V supply. The proposed RFE compares favorably to similar reported works.;Thirdly, a novel look-up table based and serial-parallel scheduled th-rotation LDPC encoder/decoder pair is proposed and implemented. By the use of novel reading/writing address mapping scheme, combining with optimized normalized min-sum decoding algorithm, the LDPC encoder and decoder circuit resources are greatly reduced and much easier to realize. In addition, the proposed architecture is implemented with 1968 code length, 1/2 code rate, 6-bit quantization and 10 times iteration on a Xilinx Virtex4 XC4VLS200 FPGA kit, compiled with ISE design suite. The synthesis results also prove the feasibility of proposed approach with not only promising BER-SNR performance, but also extremely simplified decoding scheme and circuit resources usage.;At last, combining all of novel techniques mentioned above, we implemented two IBC applications-audio player and image transmission. Both applications work well as expected and demonstrate the feasibility of proposed approach, which make us pretty sure about the commercialization of IBC in the near future.